


Two of a Kind

by kngsbrg (Citlalcoatl)



Category: Haikyuu!!
Genre: AKA, Alpha Miya Atsumu, Alpha/Beta/Omega Dynamics, Bottom Miya Osamu, M/M, Omega Miya Osamu, Omega Verse, Possessive Atsumu, Tiddy Love, a!tsumu, miyacest, o!samu, smut starting on chapter 3
Language: English
Status: In-Progress
Published: 2021-02-26
Updated: 2021-02-26
Packaged: 2021-03-16 00:27:48
Rating: Explicit
Warnings: Underage
Chapters: 3
Words: 5,357
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29692248
Author URL: https://archiveofourown.org/users/Citlalcoatl/pseuds/kngsbrg
Summary: Atsumu was certain that he was an alpha. It was something he could feel in trumming of the blood in his veins, when the court marched to his beat as he served the ball and tossed. It was something he simply knew, before their secondary gender results even came in.He also knew that Osamu had been born as a carbon copy of him.So it was only natural to assume they were meant to be the most fiery duo of alphas the sports world had ever seen....Except, things don’t always go like Atsumu expects them to.
Relationships: Miya Atsumu/Miya Osamu
Comments: 7
Kudos: 125
Collections: Miyacest Gift Exchange





	1. A Meal for One

**Author's Note:**

  * For [bronigiri](https://archiveofourown.org/users/bronigiri/gifts).



> ohgosh im so late to this exchange-
> 
> I'm so grateful for your patience Yuu, this one goes out to /Yuu/!
> 
> Prompts: ABO au, bottom Osamu, marking, thigh fucking and lactation
> 
> You'll get your smut in the next chapters, hope you enjoy this small intro!

It had started with Osamu skipping lunch during that day at school. 

His gluton brother _never_ skipped any meal time, and it had made even Atsumu worried for his brother. For as much as they bickered and fought and generally shat on each other, they were twins. They were meant to share everything.

A deep frown hung on bushy brows as he watched his grey-dyed brother walk away, Suna tailing after him like the stupid puppy he was. 

Then again, today was not just any day.

Today they would be going in to get their tests results. Their secondary-gender tests.

The twins had been born to an alpha father and a beta mother, it’d been a difficult pregnancy but their mother had managed to not only give birth to one healthy baby boy, but two. Apparently Osamu had come as a surprise, born a few minutes after Atsumu. And ever since they’d been small, the difference in their personalities had been palpable- what with Atsumu screaming his lungs out and Osamu falling asleep quickly after having gotten some milk. 

And so they had grown. Together, different. But still so similar. One would always cry after the other, and they couldn’t stand being apart for too long. It was only natural to assume that, whatever they’d present as in their teenage years, they would present the same.

Atsumu knew he was an alpha. It was something he could feel in trumming of the blood in his veins, when the court marched to his beat as he served the ball and tossed. When fire rose in his body while competing, when he demanded others adjust to what he wanted. 

He would present as an alpha, that much was certain.

And what was also certain, is that Osamu had been born a carbon copy of him.

So it was only natural, to assume they’d be the most fiery duo of alphas the sports world had ever seen. 

With this confidence, Atsumu marched into the infirmary room, ready to get the blood samples that would only confirm what he already knew to be true.

Osamu, with a more hesitant step, walked in right after.

*****

It took a few minutes to get the results within an envelope which Atsumu quickly tore apart. He couldn’t wait in his eagerness to confirm what he’d expected all these years. What everyone else expected of him really, with his brazen, loud personality, what other choice was there than to be an alpha? Truthfully, Miya Atsumu was one to be blessed by fate. He turned with an enormous grin on his face to look at Osamu- only to see his lackluster brother already quietly tucking in the results in his pants, getting ready to leave.

What the fuck! He hadn’t even asked him what he’d gotten! Even if it was _obvious_.

“Oi, ‘Samu!” Atsumu walked after his brother, “What’d ya get?” He asked with a grin, expecting the obvious as well. Even since they were kids they’d talk about being alphas like their father, about how they’d protect their mother, to which she’d just chuckled and ruffled their hair. Saying they were young, that they’d grow up with time.

Well, the time was now, Atsumu thought as he brimmed with energy. 

Osamu though, on the other hand, simply wordlessly handed him his own crumbled paper results.

Atsumu frowned and snatched the paper, couldn’t he just fucking tell him-? His golden-brown eyes glided around the paper and that’s- that’s when he saw it.

“What the fuck?”

  
  
The results read: Inconclusive.

_What the fuck?!_

Osamu shrugged, apparently disinterested, but Atsumu could read the veiled discontentment behind those eyes so much like his own.

“Dunno. Said these sorta results are rare, but it happens sometimes with…” he makes a pause, barely there but Atsumu hears it, “... betas.” A sigh, both annoyed and accepting at the same time. “I’ll probably have to retest in a few months, they’ll know for sure then.”

A beta?

Not an alpha- not like _, like him_?

Atsumu felt anger reach him, how dare- they were supposed to be in this together! They’ve always been, they’re basically carbon copies from each other, dammit! “Must be a mistake!” he snarled and grabbed Osamu by his arm, saying, “They didn’t do it right, c’mon let’s go back and-”

But Osamu slipped out of his touch.

“Just leave it, ‘Tsumu.” 

“Hah?!” ‘ _Leave it’, what did he mean ‘leave it’?!_ “‘m tellin ya they made a mistake. Just get back here and we’ll--!”

“No.” 

Two pairs of stubborn grey-brown eyes stared into each other.

“The fuck d’ya mean ‘no’?” Atsumu sneered. “Don’t ya care bout yer result?!”

“Maybe I don’t,” Osamu replied, “What’s it ta ya anyways?” _This is my business, not yours_ , implicit in the tight tone of his voice, usually calm eyes flashing with a warning to leave it alone.

Atsumu’s bushy eyebrows furrowed, chest rising as anger flooded his veins. They’re supposed to be always together. Why is he shutting Atsumu off now?!

“‘Course it’s my business!” he replies to the implied accusation, for they’re twins and understand each other better than anyone else. But also… they might expect more from each other than anyone else. “Can’t go ‘round havin’ a useless brother who can’t even present right!” Atsumu yelled, the whole hallway turning to look at them. Now, Osamu never hesitated to kick his ass when Atsumu was acting like this, and more than ever, he was aching to let go of his own frustration too.

But.

The fight he was expecting didn’t come. 

In fact, a hint of hurt seemed to flash through Osamu’s eyes.

“Ya really are a piece of shit, Atsumu.” 

And with that, he walked away. Leaving an unsatisfied, still angry but confused Atsumu fuming at nothing. The ring of his full name didn’t go unnoticed either.

What the fuck was wrong with him?!

Now, if the alpha were less focused on his own turmoil, he might’ve noticed Osamu was also struggling with something.

What might that be?

They’ll find out soon enough.


	2. Expect the Unexpected

**Summary for the Chapter:**

> ANNND right away, chapter 2! Still sadly no smut, just Longing

A month had come to pass ever since the rest of their classmates had gotten their secondary gender results. New tensions had risen between those who’d presented as alphas, trying to show they were the ‘stronger’ ones and fighting each other. New friendships had formed as well, and even some potential matchings had begun to happen.

Even Atsumu, despite his shitty personality, was getting attention from the newly presented omegas and betas. And he’d probably be enjoying more his time in the spotlight if it weren’t because things hadn’t been the same with Osamu since he’d gotten his ‘inconclusive’ results. They’d fought, not only more often but nastier. Atsumu probably felt abandoned, shut off by Osamu or something, and Osamu… well. He had his own concerns to deal with.

*****

Today had started like any other day. Osamu woke earlier than Atsumu, usually stirred up by his grumbling stomach demanding food. 

Except, this time... Osamu had woken up not feeling hungry at all. 

This was an oddity in and of itself, but he also felt quite tired, burrowing deep into his covers and letting sleep take him under once again.

… 

“‘SAMUU! WHY DIDN’T YA WAKE ME?” A very familiar screech reached his ears, “OI, YA LAZY ASS, WE’RE LATE!” 

_Late..? Ah, shit. School._  
  
Osamu couldn’t remember having fallen back asleep, and found himself quite disoriented even as Atsumu kept yelling and spluttering, throwing Osamu’s clothes at him. He was too out of sorts to even yell back at Atsumu, who kept blaming Osamu for their tardiness. The younger twin was already used to the oldest antics but, today, he felt an unhealthy rage rise at being blamed for everything once again.

Ever since they’d gotten their presentation test results, Atsumu had been even _more_ unbearable than usual. A feat accomplished only by the Universe’s decision to not only make his twin into a loud unapologetic asshole, but to also make him an _alpha_ . Osamu had gotten inconclusive results himself, most likely due to him being a beta, which by now he’d already made paces with. But Atsumu hadn’t. And somehow the fact that his twin wasn’t _identical_ to him in every way meant Osamu was trying to ‘grow apart’ from him or some shit like that, to be honest, not even Osamu could know all of the weird workings of his twin’s mind. And it’d only turned into a more insufferable asshole these days, who kept prodding at him to take the _test again_ , _what’s takin ya so long ta present?_ and really, they might be twins, but this was Osamu’s business and no one else’s.

And thus, his rage resulted in yet _another_ fight in the early morning.

… Which made for a rather bad start to the day.

What Osamu didn’t know was that it was only going to get worse.

*****

The light streamed in through the classroom windows as the English teacher tried to impart his knowledge to uninterested high school students. Osamu was seated at the back of the classroom, an opportunity he’d often use to try to nap unnoticed. But today, he felt rather uncomfortable. Too warm, even though the sun didn’t directly hit him, and itchy in the area where his shirt’s collar touched. He touched his neck, uncomfortable and still moody from the earlier fight, finding it clammy and hot. Or perhaps it was his hands…? They felt sweaty as well, and the itchiness wasn’t going away either, it only seemed to furrow deeper, until every part of his body touched by his clothes felt irritated by it. His breathing grew heavier, warmth spreading from his face, down his neck and torso, and lower still…

He could hear his name being called out through the fog in his mind, glazed eyes blinking at his teachers and classmates, who were all now turned looking at him. 

_Wha..?_

“Osamu-kun?”

“Hey, Miya, are you ok?”  
  


“Wait- do you guys smell that?”

“Make some room! Someone call his brother!” 

Somehow, among the haze, Osamu belatedly realized someone had grabbed him to take him to the infirmary, while one of his classmates offered to go get Atsumu. It was difficult to walk, but somehow they made it, and he was given something that made the *fire* stop and got him to sleep for a while.

…

…

“... ‘Samu?”

A soft uncharacteristic voice called out at him, grey-eyes blinking as he woke and got used to the lightning in the white room. 

After a bit, his own groggy voice replied, “Tsumu..?”

“Hey... Uh, take it easy.”

_Take it easy..? What did he have to take easy?_

“‘m I s’ck?” he slurred, still rather out of sorts by whatever they’d given him. At least he didn’t feel like he was burning from the inside anymore, but he still felt too warm… And the septic smell of the room bothered him, preferring to inch closer to where Tsumu sat on his bed. 

If he would’ve had enough wits to notice, he would’ve seen Atsumu get tense and nervous. “… Yeah, somethin’ like that. Ya… Uh...”

Osamu frowned, still rather out of it but disliking Atsumu beating around the bush.

“Wha’s wrong wi’ me?”

“Nothing’s wrong! Ya just-! Well. Ya finally… presented.” The blonde twin twiddled his thumbs where he sat, his usually overbearing gaze turned away, avoiding Osamu’s. 

Shouldn’t Tsumu be happy with that? He’d bugged Osamu for weeks about his late presentation, which had ended up in many fights and tensions as of late.

… Then again.

This wasn’t like when Atsumu had presented. It didn’t exactly seem like the ruts Atsumu had, even if they’d only been a few. Osamu’s brow furrowed, trying to lace thoughts together while still under the effects of the calming drug he’d been given. He also didn’t feel distinctly alpha. Nor what he’d come to expect from being a beta. It felt more like...

Like…

Atsumu finally turned to look at him, the same confusion being reflected on slightly-warmer brown eyes. 

Osamu felt sick. And it could be the drugs, the fact he had eaten too much for breakfast, or the realization of something he’d sensed but tried to deny over the past few months.

Denying the very fact that he was… an **Omega**.

**Notes for the Chapter:**

> HE'S AN OMEGA, WHO'D SAY?!?!
> 
> anyways, stay tuned for samu's titties getting love the next chapters~


	3. All Mine

**Notes for the Chapter:**

> ANNND HERE IS THE SMUT!
> 
> hope you like it yuu!! 
> 
> I'm thinking of adding an extra chapter after this to make up for being so late, for now I hope you enjoy this!
> 
> WARNING: EXPLICIT TWINCEST CONTENT UP AHEAD 
> 
> also keep in mind heat sex is inherently dubconnish, pls and thank you
> 
> if not your thing don't read

The twins fell into a heavy silence, the understanding dawning in both of them without even having to say any words.

“... Hey. Wanna go home?” Atsumu offered after a while, disliking to see his twin in such a confounded weak state. So what if he was an omega? He had Atsumu, an alpha, there to look after him. They’d be alright. They  _ had  _ to. 

Osamu simply grunted a wordless agreement for Atsumu to just get him out of there and bring him home.

  
For once, his shithead brother was acting as the older twin, fingers threading through grey hair as he assured him, “S’alright ‘Samu, I’ll take care of ya.” 

The newly-presented omega nodded, a little too pliant under the other’s touch. Quite honestly, he was scared. Scared of what would come now that he was… this. But a part of him, a visceral instinctual side that’d maybe always laid dormant until now, was actually grateful to have Atsumu there for him. 

Whatever may come, at least they would face it together.

*****

_ Fuck fuck fuck fuck, _ is what went through Atsumu’s mind as he took his still sorta drugged twin home. 

Yes, admittedly, he had been bothering Osamu to just present already, what was he taking so long for anyways?! Just be done with it and present as an alpha as he did!

But oh no.

The Universe and in particular Osamu never did like to make things easy for Atsumu.

For, alright, his brother  _ finally  _ presented. But nope, he did not present as an alpha, as he’d expected.

  
Nor was he actually a beta either.

HE’D PRESENTED AS AN OMEGA! RIGHT IN THE MIDDLE OF HIS CLASSROOM!

When some nameless scrub had gone to fetch Atsumu earlier, it took him a bit to really understand what had happened. But once he did, he pushed said guy out of the way as he ran to the infirmary- and boy, was he fuming when he saw exactly who was with Osamu.

Suna fuckin’ Rintarou. Newly presented alpha, sitting by his brother’s beside (Atsumu’s  _ place _ ) as if he were waiting for his  _ mate  _ or something to wake up.

Others might say Atsumu overreacted by baring his teeth and telling him to get out, but frankly, he would say he was wholly within his right to scare away any alpha who tried to get a little too chummy with his omega brother. 

His… omega… little brother…

Who was now with him back at their house. Sitting on the sofa next to him, innocently leaning against Atsumu’s shoulder as the alpha sat, spine straight and tense. His phone, laying in his other hand. 

Right. Atsumu was going to call their parents, let them know that ‘Samu had finally presented.

Yeah. 

He should... totally do that.

… As soon as Osamu stopped smelling so damn  _ good  _ !

His nostrils flared, taking in the scent his twin had just started to produce. Except… It felt like it’d always been there, softer and milder, something that’s just so uniquely Osamu. And just now, freely released. An enticing, sweet yet strong scent that seemed to call to others… A scent that reeked of freshly presented,  _ untaken _ , omega… There for any alpha to come and take.

A growl escaped his throat, the arm that was around Osamu tightening as he thought.  _ Just let them try and take my omega. _

Suddenly, a soft groggy voice called out to him, “... ‘Tsumu?” -And he crashed back into reality.

_ ‘MY’ omega _ ? That’s his brother! His younger twin brother who he should protect from others! Not think about- taking for himself!

Atsumu clenched his fist in horny desperation, and replied in a tight voice, “Yea, ‘Samu?” He should  _ really  _ make that call, what was he even waiting for..?

“... I dun’ feel too good.”

“Huh?!” He turned to look at the other, “What’s wrong?!”

“Other than bein’ in heat?” Osamu snapped at him, annoyed hazed eyes under furrowed brows, “It…” He blushed, and Atsumu shouldn’t find that delectable but he did. “... hurts in here…” Oh, and now he was touching his lower belly, over the shirt he demanded Atsumu to give him as soon as they arrived, and it was sort of tight on his chest and riding up his hips and… 

Atsumu’s hold on the phone loosened.

“Does it, now?” His voice deepened. Really, the choice had been made ever since he hesitated to call their parents. But even now, he wants to believe he’s letting Osamu decide. As if their destiny wasn’t set ever since ‘Samu was born after him. Ever since Atsumu presented as an alpha and Osamu… an omega. 

Still, Atsumu asked, “D’ya need me... ta help ya?”

He wondered if Osamu knew what it was exactly Atsumu was offering, wondered if under those heat-glazed eyes, Osamu’s mind still worked enough to understand the implications over his older brother offering to  _ help _ . 

Osamu nodded, breathing heavier as his heat seemed to rear back. A quick agreement, too quickly to seriously have thought it over. But then again, he  _ was  _ in the midst of a heat. And could an omega in such a situation even say no to an offering alpha? 

But Atsumu wasn’t just any offering alpha.

He was Osamu’s twin, his older (even if by a few minutes) brother. And he’d take care of him. 

Atsumu’s heart beat stronger. Until finally, he put the phone aside. 

This was about them, and no one else.

“... ‘Samu,” he breathes out, and Osamu oh, so responsive, whines softly at him. The temporary suppressants he was given are fading away, and isn’t Tsumu the luckiest? To have such a beautiful omega all tailor made for him, in the depths of his first heat, confused and needy. “C’me here.”

Osamu’s belly ached, a burning sensation which only seemed to grow deeper, settling at the base of his spine and making his mind all jumbled up. “Hn..? Where?”

Atsumu chuckled, “Lemme help ya,” and with that, he used all his strength to get Osamu right where he wanted him- on his lap. Osamu held onto Atsumu’s shoulders for support, legs spread to either side as he sat on top of Atsumu. His cheeks turned red as he realized the position he was in, 

“Wait, ‘Tsumu-”

“Hn~? Didn’t ya said ya wanted my help?” Atsumu asked with a teasing drawl. His pupils extended as he got drunk in Osamu’s scent, letting his alpha instincts take over and holding Osamu’s waist close to him. He drove his head forward, close to Samu’s neck and inhaled the sweet scent. His fingers pressed into Osamu’s sensible skin, “Lemme help ya… Samu…” He didn’t even wait for a reply before he let his tongue start to trace the warm skin under Osamu’s jaw, so near his mating gland…

Osamu had, admittedly, zero experience in this field, and yet his body moved on his own, hips trying to grind against his brother’s ( _ ohgod what were they doing- _ ) body. His head instinctually moved to one side, giving the alpha more room to explore, as well as ( _ unknowingly _ ) submitting. 

Atsumu’s instincts purred with contentment as he was given more room to explore, moving one hand inside Osamu’s shirt and up his trembling stomach, “Where did’ya say it hurt?” He lulled, nails raking against the skin as he made it up to Osmau’s chest. “Was it here?” He asked as he pinched a sensitive nipple. 

“Ah-no! Not there!” Osamu squirmed, “I told ya--” And he blushed, brows furrowed, too embarrassed to truly say exactly  _ where  _ he wanted Atsumu. Oh well, if he didn’t want to admit then Atsumu could keep having fun with his twin’s heat-sensitive body. 

A sly fox grin formed in Atsumu’s mouth, as he forcibly turned Osamu’s shirt up and bared his chest. Osamu had always tended to carry a few more pounds than Atsumu, probably due to his gluton nature. But it might also be, as Atsumu now fully appreciated, that all that weight went to ‘Samu’s tits. He’d called them like that once and gotten punched in the face, but now that Osamu was fully into heat and  _ needed  _ him. Well, he couldn’t exactly do anything to him now, could he? 

“I dunno ‘Samu, it looks sorta swollen.” Atsumu’s fingers pinched at the rosy buds. And well, he wasn’t completely wrong. His chest did seem to carry more swell than usual. His thumbs drew slow circles around his nipples, noticing with delight how responsive Osamu was to even this kind of stimulation.  _ I wonder if he can cum just from this…? _ Atsumu’s mind jot that down for later. 

Osamu’s hold on Atsumu’s shoulder tightened, mouth dropping open at how even this tiny touch electrified his whole body, even his dick seemed to stir, more wetness forming on his behind. 

“Ye--ugh, yer a dick…” 

“So I’ve been told,” is all Atsumu said before drawing near and sucking on the nipples he’d stimulated into standing erect. He sucked and nipped at one of it while he pinched the other. Osamu seemed unsure whether to pull closer or away, needing the other’s touch but knowing that’s not quite what he actually  _ needed _ . 

“Tsumu,” the omega whined, his school pants getting wetter as his lower body grew more desperate for attention. “Not there!”

“Then where?” Atsumu said, breathing into the poor nipple he’d bitten into redness. 

“I…” Osamu swallows, shallow breathing as he tries to put his thoughts together. “I need ya…” he grabs Atsumu’s hand and places it at his own lower back, body burning as the redness spreads down his face into his neck and chest, even the tips of his ears are blushing. “... down here.” He says, too embarrassed to look at Atsumu’s eyes and simply burrows his face in the other’s neck. “Ya asshole…” 

Atsumu’s eyes grew wider when his nose finally caught a whiff of the slick being produced by the omega’s arousal. Quickly, too eager to keep fooling around, he pushed his hand down Osamu’s pants and- found exactly what his nose had smelled. 

“ _ ‘Samu _ .” He growled, hand pushing the small of Osamu’s back closer to him and into an arch that pushed his ass further up, fingers slipping between the wet cheeks of Osamu’s ass. “‘s this where ya need me?”

The omega simply shuddered, _ yes yes, there- it hurts right there-  _ “‘ve been tellin ya-”

“I wanna see.”

_ Huh? _

Before Osamu’s clouded mind could understand, Atsumu was pushing him against the sofa and undoing his pants, hurried in a way Osamu’s body could fully understand. He lifted his hips to be freed from the constriction of his school clothing and- finally, his trembling legs and hardened dick were revealed.

But Atsumu’s eyes were caught up somewhere in particular.

“Yer so… wet… how’re ya so wet down here,” Atsumu marveled, fingers prodding at Osamu’s soft slick thighs. 

Osamu whined, heat taking over as his legs fell open, too caught up in his arousal to put any thought into how lewd that made him look. “S-shuddup ‘n hurry…”

That made Atsumu’s brain whirr and stop for a second there. _ Wait. Samu wants me to… to…  _ His face burned bright red, mind still blank as his body moved on his own and pried Osamu’s legs further apart, golden gaze locked at the spot where Samu’s slick was sliding out from, all pink and flushed, asking to be filled.

Asking for him.

“Tsumu..!” Samu’s protest made it known that he said that out loud. Oh well.

He slid his tongue agsint his lower lip, “Imma suck ya, ‘Samu.”

“Wai-”

He didn’t wait, he tended to use his tongue often to express himself, but today. Today it has found its true calling. He pushed Samu’s leg up and his own body down, bending his twin till his ass was left dangling in the air, as if presenting itself just for him.  _ Hm, ‘Samu presentin’ fer me…  _ is a thought he also saved for later, tracing his twin’s skin with his tongue, first licking at the slick that dripped down his thighs, and moving up till he finally found the source.

Osamu’s hole was warm and pliant to his touch, giving way to Tsumu’s tongue. The taste was so  _ uniquely  _ ‘Samu and Tsumu hungered for more of it. 

“Hn--hah…”

He heard Samu moan above him, which only spurred him to keep licking and sucking, wanting to hear more of his twin’s noises. 

“Hold yer legs up.” The alpha didn’t wait for Samu to do as he says- he knew he would obey, and freed up one of his arms to direct one of his fingers towards Osamu’s hole.

“AH!”

“Yer so warm’ Samu…” Tsumu murmured, his own need taking hold of him, as he put all of his focus in unraveling the  _ omega  _ opened up so prettily before him. “D’ya like this?”  _ D’ya need this? _ , he asked and thought, without waiting for an answer before he put another finger inside, exploring ‘Samu’s insides and claiming this unexplored territory for himself. He plied his fingers apart to stretch the other further- not that he actually needs it. “Yer so loose, I could put my whole hand inside.” 

Maybe he was exaggerating, but ‘Samu didn’t know that, whining and blushing deeper at Tsumu’s filthy words. But who knows, maybe they could do it if they worked hard at it. But that’ll have to be another time. For now Tsumu used that space to put his tongue in, greedily sucking more of Samu’s juices out. He licked and prodded noisily, which only served to embarass Samu further but fuck- he couldn’t complain when it felt that damn good.

“Tsu--Tsumu!”   
  
“Yea, baby?” Atsumu drawled, licking Samu’s juices off his lips, fingers twisting inside the other, seeking the spot he knew would drive the other crazy.

“Hurry already...” Osamu whined, holding his own legs open for the other- it should embarrass him, looking like a whore in heat, but he just needed- needed  _ more _ .

“What’d ya want me ta do?” The alpha teased, enjoying way too much how the heat turned his brother into a needy slut. “Ya gotta say it.” 

The omega’s need burned deep in him, and Atsumu’s fingers weren’t nearly enough to fill it. “Just- knot me, ya piece o’ asshole.” He said through gritted teeth, hold tightening on Atsumu’s hair as a warning.

“Mhm, we’ll work on ya askin’ nicer.” Atsumu said with a grin, pushing himself up and hurrying to take his own throbbing dick out of his pants. Admittedly, he was sort of nervous. He’d never done this before. His fingers slipped out as he used his hand to angle himsef. The messy haired blonde took a look at Osamu, “Ya ready?”

Was he ready to get fucked by his own twin? Mentally, probably not. But physically, he  _ ached  _ for it. So he let go of his legs to instead hold onto Atsumu’s shoulders. “Just do it.” 

Atsumu nodded, taking that as permission, and put the head of his cock, heavy and flushed, against Osamu’s throbbing hole. He bit his lip as he tried to go slow at first, but his eagerness was too much to really wait for Osamu to adjust. “Fuuck… ya feel so… good…” He never thought Osamu’s insides could be so hot and wet, all ready for his cock to fill. 

Osamu shut his eyes tight as he grew used to the pressure inside him, it shouldn’t be possible for him to take a cock so easily, not on his first time… Then again, maybe omegas were made for this. At least he felt like he was. The moment Atsumu’s dick finally entered him he felt the burning need ease some. But not fast enough.

He wrapped his legs around Atsumu’s waist and pulled him even  _ deeper _ . 

“Hnn- move.”

Atsumu didn’t need to be told twice. He held his body above Osamu’s with one arm, while he used the other to pull one of the omega’s legs up. 

“Just remember ya asked fer it.”

Is all Atsumu says as a warning, eyes flashing with the same intense right before destroying the opposite team in the court, except his focus was now wholly turned in fucking Osamu’s brains out. He withdrew and then slammed hard and deep into his twin’s ass, reveling in Osamu’s choked noise before pulling back and doing it again. And again. He didn’t give Osamu any time to catch his breath. Not that the whore needed it anyways. He was drooling and murmuring incoherently at Atsumu to give him  _ more _ . And Atsumu happily did. He could feel his knot forming, spurred by the omega pheromones being released into the air. He didn’t even think of the fact they aren’t wearing any protection, he just wanted to fill Osamu with his cum till he’s bulging with it. 

“Tsumu!” Osamu was moaning, utterly overwhelmed, and Atsumu’s gaze was drawn to those pretty lips. They’re already fucking, so what’s to add more to it? He leaned down and put his mouth against Osamu’s. It’s not the first time they’ve kissed, but it is the first time they do it knowing exactly what it means. Atsumu used his tongue to bully Osamu’s mouth open, drinking in his sounds and moans as his knot began to press against Osamu’s entrance. 

“Open up fer me.” He demanded, trail of spit connecting their red lips as he drove his hips harder, grabbing both of Osamu’s legs and prying them apart so he wouldn’t miss the exact moment his knot finally slipped into the other. 

“Hn--but we--” Osamu’s jumbled up mind tries to remember something  _ important _ , isn’t it dangerous for Tsumu to cum inside him just like that..? But ah. He can’t remember why. And Atsumu’s hands are moving to his ass and spreading his cheeks wide. 

“Ya want my knot ‘er not?” Atsumu growls, and Osamu’s instincts scream at him to  _ take it _ . This is what he needs. 

And so, finally, Atsumu’s engorged knot slips inside Osamu and locks them together. 

It seemed to be the only piece missing.

The knot pressed up against his prostate and with every tug his body trembles, tensing and spasming right before he releases- at the same time Atsumu finally spilled inside him with a groan. 

“Ah-AH!” Osamu threw his head back as his orgasm took over him, his own  _ -untouched-  _ dick releasing over his stomach and chest in spurts. 

Atsumu kept moving his hips, stimulating his knot to keep cumming inside of ‘Samu as long as he can. His gaze is caught by the neck gleaming with sweat right before him, and he bared his teeth- letting instinct take over him as he bit into Osamu, holding him still by his neck as he filled him with his cum. 

“W-wai--Tsum...u!”

Ah, his baby brother probably thought Atsumu had mated him right here and there. But nah, that’d come later. When they were ready to be independent and moved in together. He licked the red mark he’d left on Osamu’s neck, and moved to bite him on the other side. 

“Keep still ‘Samu,” Atsumu murmured against the hot skin. They’d be stuck together for a while, Atsumu’s knot was still quite full and he didn’t know how long it’d take till it went down. “Rest up.” He ordered, tugging them into a more comfortable position for them to lay for the next possible couple hours to come. 

Osamu could feel the exhaustion dawn on him. The heat had taken a big toll, but finally his body -now that they were knotted and full- was allowing him to rest. He supposed he could deal with whatever they’d done after taking a quick nap.

On the other hand, Atsumu licked his lips, still quite energized. He could have some fun while ‘Samu laid there quiet and asleep. There was a lot of time to kill after all, and a lot of unmarred skin he could mark. 

_ Lucky him indeed. _

  
  
  


**Notes for the Chapter:**

> wouldn't we all be lucky to make samu into our omega bitch hhhh lucky tsumu inDEED
> 
> comment if you want an extra smutty chapter <3


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